Patent attributes
A battery ECU estimates the SOC by integrating the battery current measured by a current sensor, and the battery voltage Vnis measured by a voltage sensor, and the battery temperature Tnis measured by a thermometer if the fluctuation of the charging/discharging current is great. If the number m of estimations of SOCnis m≦10, m is incremented. The battery internal resistance Rnis estimated from the measured battery temperature Tnby using a correlation map showing the correlation between the previously stored battery temperature T and the battery internal resistance R. An estimation charging/discharging current Inis determined using the measured battery voltage Vn,the battery open voltage Vocvn-1determined on the basis of the previously estimated charged state, and the estimated battery internal resistance Rn. The SOCnis estimated by integrating the estimated charging/discharging current In. If the number m of estimations of the SOCnis m=10, the number m of estimations is changed to 0. The charging/discharging current inis measured by a current sensor. The battery internal resistance Rnis calculated from the battery voltage Vnand the charging/discharging current in. The battery temperature Tnis also measured, and the T-R correlation map is corrected
